Microstrip and coplanar design considerations for microwave bandwidth PIN-HEMT optical receivers

Optical fibre systems which operate in the multi-Gbit/s regime or utilise microwave subcarriers require low noise receivers with bandwidths spanning many GHz. Such receivers may be realised with hybrid circuits using discrete devices mounted on microstrip or coplanar substrates. The paper shows that the microstrip approach takes advantage of a broad library of well established CAD models, however certain difficulties can arise in the practical realisation of receivers. These difficulties are avoided in the coplanar approach, which generally realises a broader bandwidth, but CAD models are less well developed. In either case it is shown that a simple hybrid construction may be used to produce high performance optical receivers